1. Field of the Invention
The present invention relates to a method of forming a fine pattern in which a pattern interval of a resist pattern or a hole diameter is narrowed, and a developing/washing device used for the same, and further, to a plating method (hereinafter referred to as a frame plating method) for forming a plating film by using a mold formed by patterning a resist, and a manufacturing method of a thin film magnetic head provided with an induction type magnetic head as a recording head.
2. Description of the Related Art
A composite type thin film magnetic head including a magnetoresistive (MR) head used for data reproduction and an induction type magnetic head used for data recording is used as a magnetic head of a magnetic disk device.
The MR head includes any one of an AMR (Anisotropic Magnetoresistive) component using an AMR effect, a GMR (Giant Magnetoresistive) component using a GMR effect, and a TMR (Tunneling Magnetoresistive) component using a tunnel junction film indicating a magnetoresistive effect. As the surface recording density of a magnetic recording medium becomes high, a component to be used is changed from the AMR component to the GMR component, and further, to the TMR component.
As one factor for determining the performance of the MR heads, there is optimization of MR height. The MR height is a height of the MR component from an end portion at a side of an air bearing surface (ABS) opposite to a magnetic recording surface of a magnetic recording medium to an end portion at the opposite side, and this height depends on an amount of polishing of the ABS surface in a head manufacturing process.
The induction type magnetic head realizes a ring structure having a narrow gap by a semiconductor process, and includes upper and lower magnetic poles which are laminated through an insulating film and has a gap (write gap) at the side of the ABS surface to form a closed magnetic path, and a thin film coil formed in the insulating film between the upper and lower magnetic poles. A head material is magnetized to high magnetic flux density by a recording current flowing through the thin film coil, and predetermined leakage magnetic field is formed over the gap to record data on the magnetic recording medium.
As one factor for determining the performance of the induction type magnetic head, there is optimization of throat height (TH). The throat height is a height of the magnetic pole from the ABS surface to the end portion of the insulating film, and this height also depends on an amount of polishing of the ABS surface in the head manufacturing process. In order to improve the head efficiency of the recording head, it is necessary to make the throat height as small as possible.
In order to raise the recording density, it is necessary to raise the track density of the magnetic recording medium. For that purpose, it is necessary to realize a recording head in which a magnetic pole width and a gap width at the ABS surface are made narrow, and a semiconductor processing technique is used for realizing this.
The foregoing composite type thin film magnetic head is manufactured through a plurality of manufacturing processes, for example, a sputtering process, a photolithography process, a frame plating process, an etching process, a polishing process, and the like. Herein after,an example of a manufacturing method of the thin film magnetic head will be described in brief.
First, an Al2O3TiC substrate having high hardness and excellent in wear resistance is used. When the magnetic head is completed, this substrate itself functions as a slider body of the magnetic head. The reason why the substrate having high hardness and excellent in wear resistance is used is to secure floating accuracy of the head and to obtain accurate MR height and throat height.
A film having high adhesiveness, for example, a chromium film is formed on the Al2O3TiC substrate by sputtering or the like. Next, a lower shield layer made of, for example, Permalloy is formed. Next, an MR component interposed between insulating films is formed on the lower shield layer.
Next, an upper shield layer made of Permalloy or the like is formed. By this, an MR head for reproduction is completed. The upper shield layer is also used as a lower magnetic pole of an induction type magnetic head for recording.
Next, an insulating film for formation of a gap is formed on the lower magnetic pole, and further, an insulating film is formed, and then, a film excellent in adhesiveness to an oxide, for example, a chromium film is formed thereon by sputtering or the like. Next, there is formed a thin film of, for example, copper, which becomes an electrode film when a frame plating method is used. Next, a copper coil of a first layer is formed by the frame plating method. As the need arises, coils of second to third layers are also formed in the same way.
After the formed thin film coil is embedded by an insulating film, an upper magnetic pole made of, for example, permalloy is formed thereon by using the frame plating method. A recording gap layer is formed by carrying out etching, while the upper magnetic pole at the side of the ABS surface is used as a mask. The upper magnetic pole is formed so that it is connected to the lower magnetic pole through the coil at the opposite side of the recording gap layer so as to constitute a closed magnetic path. A protective film is formed on an upper layer of the upper magnetic pole, and the film forming process is completed.
Next, the Al2O3TiC substrate is cut into rod-like substrates including several tens heads. The ABS formation surface of the rod-like substrate is polished to provide the throat height of a height of several xcexcm. After the ABS surface is formed, the rod-like substrate is cut, so that a plurality of thin film magnetic heads are completed. In the manufacturing method of the thin film magnetic head as described above, the frame plating method is used for the formation of the thin film coil or the formation of the upper magnetic pole.
A conventional frame plating method will be described in brief with reference to FIGS. 9A to 9E. The frame plating method is a method of patterning a plating film by using a mold formed by patterning a resist, as disclosed in, for example, Japanese Patent Publication No. S56-36706.
FIGS. 9A to 9E are sectional views showing a manufacturing process of a plating film using the conventional frame plating method. As shown in FIG. 9A, an electrode film 502 is formed on an insulating substrate 500 by using a sputtering method or an evaporation method. At a lower layer of the electrode film 502, an adhesive layer, for example, a Cr (chromium) film or a Ti (titanium) film, may be formed to raise the adhesiveness to the insulating substrate 500. Although there is no problem when the electrode film 502 is made of a material having conductivity, if possible, it is desirable to use the same material as a metal material to be plated.
Next, as shown in FIG. 9B, a resist is coated on the whole surface to form a resist layer 504, and as the need arises, a prebake treatment of the resist layer 504 is performed. Next, exposure light is irradiated through a mask 506 on which a predetermined pattern is drawn, so that the resist layer 504 is exposed.
Next, as the need arises, a heat treatment is performed, and then, development is carried out by an alkaline developing solution. As the alkaline developing solution, for example, tetramethylammonium hydroxide (TMAH) of a concentration of 2.38 wt % is used. Next, the developing solution in the resist layer 504 is washed by a washing solution, and a development dissolving reaction in the resist layer 504 is stopped, so that resist frames 508 patterned into a predetermined shape are formed (see FIG. 9C).
Next, the substrate 500 is immersed in a plating solution 512 in a plating bath, and a plating process is carried out using the resist frames 508 as a mold, so that plating films 514 are formed between the resist frames 508 (see FIG. 9D).
Next, as the need arises, water washing and drying are carried out, and then, the resist frames 508 are peeled off from the substrate 500 by using an organic solvent. Next, the electrode film 502 is removed by dry etching (ion milling, reactive ion etching (RIE), etc.) or wet etching while the plating films 514 are used as a mask (see FIG. 9E). The above is an outline of the frame plating method. Like this, the frame plating method is a technique for forming the plating films 514 of a predetermined shape using the resist frames 508 obtained by patterning the resist layer 504 as a mold.
In recent years, as the surface recording density becomes high, a track width of a thin film magnetic head increasingly becomes narrow, and as a result, it becomes necessary to form an upper magnetic pole so that a very narrow magnetic pole width can be obtained. To this end, it is necessary to narrow a trench width between resist frames when an upper magnetic pole is formed by the frame plating method.
As means for realizing narrowing of an interval between the resist frames, there is a fine pattern forming method disclosed in, for example, Japanese Patent Unexamined Publication No. H06-250379, Japanese Patent Unexamined Publication No. H10-73927, or Japanese Patent Unexamined Publication No. H11-204399. In this fine pattern forming method, the surface of a resist pattern containing a material generating acid by heating or light irradiation is covered with a resist (fine pattern forming material) containing a material which is cross-linked by the existence of acid. Acid is generated in the resist pattern by heating (mixing bake) or light irradiation, and a cross-linked layer generated on an interface is formed as a covering layer of the resist pattern, so that the width of the resist pattern is thickened. By this, the interval between the resist patterns can be narrowed.
This fine pattern forming method will be described in brief with reference to FIGS. 10A to 10E. First, as shown in FIG. 10A, after a first resist layer 530 which includes a mechanism for generating acid in the inside by a suitable heat treatment, is coated on a substrate 500 by spin coating or the like, prebaking is carried out as the need arises. Next, in order to form a first resist pattern, the first resist layer 530 is exposed through a mask on which a predetermined pattern is drawn.
After the first resist layer 530 is exposed, postbaking is carried out as the need arises, and an alkaline solution such as TMAH is used as a developing solution to carry out development. Next, the developing process successively shifts to a washing process. The developing solution in the resist layer 530 is washed by a washing solution, and a development dissolving reaction in the resist layer 530 is stopped, so that as shown in FIG. 10B, a first resist pattern 532 patterned into a predetermined shape is formed. Incidentally, as the washing solution, for example, pure water is used. When the washing is ended, the washing solution is blown away and the substrate 500 is dried.
Next, as shown in FIG. 10C, a soluble second resist layer 534 containing a cross-linking material, which is cross-linked by the existence of acid, as its main ingredient and being dissolved in a solution, which does not dissolve the first resist pattern 532, is coated on the substrate 500. Next, after the second resist layer 534 is coated, prebaking is carried out as the need arises.
Next, as shown in FIG. 10D, the first resist pattern 532 formed on the substrate 500 and the second resist layer 534 formed thereon are subjected to mixing baking to accelerate diffusion of acid from the first resist pattern 532, and the acid is supplied into the second resist layer 534, so that a cross-linking reaction is generated at the interface between the second resist layer 534 and the first resist pattern 532. A cross-linked layer in which the cross-linking reaction has been generated by this mixing baking is formed in the second resist layer 534 so as to cover the first resist pattern 532.
Next, after the second resist layer 534 which has not been cross-linked is removed by using a developing solution, washing is carried out. A washing solution, for example, pure water is sprayed onto the surface of the substrate 500 to carry out the washing, and as shown in FIG. 10E, a second resist pattern 536 in which the first resist pattern 532 is covered with the cross-linked layer is formed.
The second resist pattern 536 formed through the above processes becomes a resist pattern in which a hole inner diameter of a hole pattern and a separation width of a line pattern are narrower than the first resist pattern 532.
When the resist frame which is formed by the foregoing fine pattern forming method and in which the interval is narrowed, is applied to a frame plating method in a manufacturing method of a thin film magnetic head, there occurs a possibility that an upper magnetic pole having a fine width can be formed.
However, when the upper magnetic pole of the thin film magnetic head is formed by the frame plating method, since undulations having a relatively large difference in height are produced in a coating region of the resist layer, a locally very thick resist layer is formed. Since a pattern of a relatively very thin line width is formed to this thick resist layer, a resist frame having a high aspect ratio is formed. Besides, there also occurs a state where a frame film thickness is extremely thick with respect to a width of a trench between the resist frames.
Even if a fine pattern forming material is coated on the resist frame in this state, the fine pattern forming material does not permeate to the bottom of the trench, and there occurs a disadvantage that a covering layer is not uniformly formed on the side wall of the resist frame. This disadvantage remarkably occurs at the side wall of the resist frame especially at the bottom of the trench, and it becomes remarkable as the aspect ratio (ratio of a thickness of a resist layer to a trench width) of the trench pattern becomes high.
Further, if the aspect ratio of the trench pattern is high, even if a prewet treatment in which a hydrophilic treatment, such as water treatment or surface active agent treatment, is performed on the surface of the resist frame, is carried out before the fine pattern forming material is coated on the resist frame, this disadvantage is not improved.
An object of the present invention is to provide a fine pattern forming method in which a fine pattern forming material can be certainly formed on the surface of a resist pattern even if a film thickness of the resist pattern is very large as compared with a width between the resist patterns.
Another object of the present invention is to provide a developing/washing device suitably used for a fine pattern forming method in which a fine pattern forming material can be certainly formed on the surface of a resist pattern even if a film thickness of the resist pattern is very large as compared with a width between the resist patterns.
Still another object of the present invention is to provide a frame plating method using a fine pattern forming method in which a fine pattern forming material can be certainly formed on the surface of a resist pattern even if a film thickness of the resist pattern is very large as compared with a width between the resist patterns.
Still another object of the present invention is to provide a manufacturing method of a thin film magnetic head using a frame plating method using a fine pattern forming method in which a fine pattern forming material can be certainly formed on the surface of a resist pattern even if a film thickness of the resist pattern is very large as compared with a width between the resist patterns.
The above object is achieved by a fine pattern forming method characterized by coating a resist, which contains a material generating acid by heating or light irradiation, on a substrate, exposing the resist through a pattern and developing the resist, washing a developing solution out with a washing solution to form a resist pattern, coating a fine pattern forming material containing a material, which is cross-linked by existence of acid, on the substrate in a state where the washing solution is adhered to the substrate, generating acid in the resist pattern by heating or light irradiation, covering the resist pattern with a cross-linked layer generated on an interface between the resist pattern and the fine pattern forming material, developing a not-cross-linked layer of the fine pattern forming material by a developing solution for the fine pattern forming material, and washing the developing solution out with a washing solution.
The above fine pattern forming method of the present invention is characterized in that the substrate is not dried in a period from development of the resist pattern to coating of the fine pattern forming material.
Besides, the above object is achieved by a developing/washing device characterized by comprising a developing solution nozzle for spraying a developing solution for development of an exposed resist layer formed on a substrate, a washing solution nozzle for spraying a washing solution for washing the developing solution out, a fine pattern forming material spray nozzle for spraying a fine pattern forming material onto a surface of the substrate in a state where the washing solution is held without being dried after washing, and a fine pattern forming material developing solution spray nozzle for spraying a developing solution for the fine pattern forming material.
Further, the above object is achieved by a plating method characterized by forming an electrode film on a substrate, coating a resist, which contains a material generating acid by heating or light irradiation, on the substrate, forming resist pattern by exposing the resist through a pattern and developing the resist, washing a developing solution out with a washing solution, coating a fine pattern forming material containing a material, which is cross-linked by existence of acid, on the substrate in a state where the washing solution is adhered to the substrate, generating acid in the resist patterns by heating or light irradiation, covering the resist pattern with cross-linked layer generated on interface between the fine pattern forming material and the resist pattern, developing a not-cross-linked layer of the fine pattern forming material by a developing solution for the fine pattern forming material, washing the developing solution out with a washing solution, immersing a surface of the substrate in a plating solution, and forming a plating film between the covered resist patterns.
Furthermore, the above object is achieved by a manufacturing method of a thin film magnetic head, which comprises a plating process for forming a plating film by using a mold formed by patterning a resist and is characterized in that the plating process includes the plating method of the present invention.